1. Field of the Invention
The present invention relates to aerial delivery systems, and, more particularly, to parafoil-based payload delivery systems.
2. Description of the Related Art
Maneuverable ram-air parafoils are widely used today. The list of users includes skydivers, smoke jumpers, and specialized defense forces. The extended range of ram-air parafoils compared to round parachutes makes ram-air parafoils very practical for payload delivery. Further, the touchdown accuracy requirement for parafoil-based systems should be much tighter that round parachutes, but it largely depends on a guidance, navigation and control (GNC) unit to produce and execute the corresponding steering commands.
Recent introduction of the Global Positioning System (GPS) made the development of fully autonomous ram-air parafoils possible. Autonomous parafoil capability means delivery of the parafoil system, typically including a payload, to a desired landing point, e.g., a target, from a release point using an onboard computer, sensors and actuators. A navigation subsystem manages data acquisition, processes sensor(s) data, and provides guidance and control subsystems with information about the parafoil. Using this information along with local wind profiles, the guidance subsystem determines the delivery and generates a feasible descent trajectory all the way down to the desired impact point, i.e., the target. The control subsystem tracks this trajectory using the information provided by the navigation subsystem and onboard actuators.
Introduction of the GPS (Global Positioning System) allowed the development of fully autonomous different-weight aerodynamic decelerator systems. Realistically, it was desirable to have payloads aerially delivered from large standoff distances with persistent <100 m circular error probable (CEP) accuracy. Accordingly, during the last decade, several GNC concepts for gliding parachute applications have been developed and tested. Specifically, some systems were demonstrated during Precision Airdrop Technology Conference and Demonstrations (PATCAD) held at the U.S. Army Yuma Proving Ground, Yuma, Ariz., e.g., PATCAD-2001, PATCAD-2003, PATCAD-2005, PATCAD-2007, and PATCAD-2009, and Precision Airdrop Demonstration Capability PCAD-2006 and PCAD-2008 held near Bordeaux, France. However, touchdown accuracy of parafoil systems was still problematic, especially with small parafoils having light weight payloads. Accurate delivery of a light-weight payload (10-15 pounds) with a small parafoil on target was very difficult because small parafoils are very sensitive to wind, e.g. the trajectories are easily impacted by wind.